Infeed, changing current direction, .
One to keep in mind on a ring bus is that you don't know how the current is going to go around the ring since there is very little impedance. I have seen weird splits on the phases. I have seen phase to phase faults produce splits that look like zero sequence currents on some CTs due to how the fault current pathed around the ring bus. When you have two paths on a bus to a fault, you will not know how the current will splits If you have one path to the fault or a appreciable amount of impedance on each path so that slight variations due to connection impedance, spacing, or equipment don't significantly change the flows, then it will be more predictable. So, I don't even think it is really doable with a single source on a ring bus.
At the transmission level,which is not at all single sourced, there are a lot of compromises made to coordinate ground time overcurrent at the transmission level. Enough so that I often questioned the point of even coordinating time overcurrent curves if it is going to take 1-2 seconds (an eternity at the transmission level) for them to operate and that will only happen if the communication assisted scheme fails. Some utilities use ground distance as the primary ground protection and ground overcurrent just as a really slow backup that doesn't necessarily need to coordinate.
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If you can't explain it to a six year old, you don't understand it yourself.